Note: Descriptions are shown in the official language in which they were submitted.
CA 02747894 2016-01-13
77691-109
METHOD FOR THE DELIVERY OF A MULTI-COMPONENT
REACTIVE SYSTEM TO A MOLDING OPERATION
FIELD OF THE INVENTION
[0001] This invention relates to molding operations. In one aspect, the
invention relates
to the formation of articles through the use of injection molding techniques
while in another
aspect, the invention relates to the formation of such articles in a manner
that allows for off-
mold curing. In yet another aspect, the invention relates to a method of
feeding a two-
component reactive system to an extruder designed for limited mixing while in
still another
aspect, the invention relates to a method of forming a mix of a base compound
and a catalyst
prior to feeding the mix to an extruder.
BACKGROUND OF THE INVENTION
[0002] Siloxane-modified polyolefin elastomers are under development for
use in the
manufacture of power cable accessories, e.g., cable joints, splices, separable
connectors,
cable termination, etc., by injection molding. These new polymers offer the
possibility of
injecting thick parts in a thermoplastic mode, de-molding the part, and
storing it for latent
cure off-mold under ambient conditions, i.e., without the need for external
moisture or heat.
This approach has the potential of substantially cutting the manufacturing
cycle time for
making these parts.
[0003] This new technology is a two-component system comprising (1) a
polyolefin
containing silane functionality in combination with a hydroxy-terminated
silicone polymer,
or a blend of a vinyl silane, polyolefin, peroxide and a hydroxy-terminated
silicone polymer,
and (2) a catalyst masterbatch, i.e., a catalyst carried in a suitable base
polymer. These
1
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
components need to be adequately blended with one another in a melt mixing
operation prior
to the injection step to ensure efficient and uniform crosslinking.
[0004] One potential challenge for the implementation of this technology is
that the
current injection molding manufacturing process relies on rubber injection
molding
equipment in which the material is first roll-milled and then shaped into a
strip, i.e., tape, for
feeding into an extruder mounted on the molding machine. These machines are
typically
fitted with rubber extruders which are designed for simple masticating and
pressurization.
These extruders are typically short in length, and thus have limited, if any,
mixing capability.
[0005] Accordingly, a need exists for a method by which the reactive base
compound and
catalyst masterbatch are delivered to the injection molding machine without
equipment
modification and with minimum interaction between the two components prior to
feeding to
the molding machine so as to avoid premature reaction (scorch) of the
components in the
melt.
SUMMARY OF THE INVENTION
[0006] In one embodiment the invention is a tape comprising (A) a first
ribbon
comprising a first compound, and (B) a second ribbon comprising a second
compound, the
second ribbon carried on the first ribbon and the first and second compounds
reactive with
one another under ambient conditions, e.g., 23 C and atmospheric pressure. In
one
embodiment the first compound is a crosslinkable resin, e.g., a polyolefin
comprising cure
sites, and the second compound is a catalyst that promotes the cure of the
crosslinkable resin
under ambient conditions.
[0007] In one embodiment the invention is a tape comprising (A) a first
ribbon
comprising (1)(a) a polyolefin containing at least one silane functionality,
and (1)(b) a
hydroxy-terminated silicone polymer, or (2) a blend of a vinyl silane,
polyolefin, organic
initiator, e.g., a peroxide, and a hydroxy-terminated silicone polymer, and
(B) a second
ribbon comprising a catalyst masterbatch, the second ribbon carried on the
first ribbon. In
one embodiment the first and second ribbons are in direct contact with one
another while in
another embodiment, the first and second ribbons are separated by a third
component,
typically a third ribbon intermediate between the first and second ribbons. In
one
embodiment, the third component is an adhesive. In one embodiment the third
component is
2
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
a barrier resin. In one embodiment the third component is both an adhesive and
a barrier
resin.
[0008] In one embodiment, the first ribbon comprises a groove shaped and
sized to
receive and hold the second ribbon. Preferably the groove is in the machine
direction of the
tape, and the groove can be continuous or intermittent. In other embodiments
the peroxide
may reside in the second and/or third ribbon in addition to or in substitution
for residing in
the first ribbon.
[0009] In one embodiment the invention is a process for making a tape
comprising (A) a
first ribbon comprising (1)(a) a polyolefin containing at least one silane
functionality, and
(1)(b) a hydroxy-terminated silicone polymer, or (2) a blend of a vinyl
silane, polyolefin,
organic initiator and a hydroxy-terminated silicone polymer, and (B) a second
ribbon
comprising a catalyst masterbatch, the second ribbon carried on the first
ribbon, the method
comprising the steps of (i) forming, e.g., extruding, the first ribbon, (ii)
forming, e.g.,
extruding, the second ribbon, and (iii) joining, e.g., physical compression,
chemical adhesion,
etc., the first and second ribbons. In one embodiment the first and second
ribbons are
co-extruded. In one embodiment the first ribbon is extruded with a machine-
direction groove
and allowed to solidify, and then the second ribbon is formed (e.g.,
extruded), solidified, and
then fitted into the groove of the first ribbon, with or without the aid of an
adhesive. In one
embodiment a third component is placed between the first and second ribbons.
In one
embodiment all three components are co-extruded and joined to one another in a
single
operation.
[0010] In another embodiment the invention is a tape comprising (A) a
ribbon
comprising (1)(a) a polyolefin containing at least one silane functionality,
and (1)(b) a
hydroxy-terminated silicone polymer, or (2) a blend of a vinyl silane,
polyolefin, organic
initiator and a hydroxy-terminated silicone polymer, and (B) a second
component comprising
a catalyst masterbatch dosed, i.e., sprayed, onto the ribbon. In one
embodiment the catalyst
masterbatch is dosed onto the ribbon just prior to feeding the ribbon into an
extruder.
[0011] In one embodiment the invention is a multilayered tape comprising
(A) a first
layer comprising (1)(a) a polyolefin containing at least one silane
functionality, and (1)(b) a
hydroxy-terminated silicone polymer, or (2) a blend of a vinyl silane,
polyolefin, organic
initiator and a hydroxy-terminated silicone polymer, and (B) a second layer
comprising a
3
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
catalyst masterbatch, the second layer carried on the first ribbon, and (C)
optionally an
intermediate layer between the first and second layers. In one embodiment the
intermediate
layer comprises a material that is not porous to the materials of the first
and second layers
and thus serves as a barrier layer between the first and second layers.
[0012] In one embodiment the invention is a process for making injection
molded
articles, the process comprising feeding into an injection molding machine a
tape comprising
(A) a first ribbon comprising (1)(a) a polyolefin containing at least one
silane functionality,
and (1)(b) a hydroxy-terminated silicone polymer, or (2) a blend of a vinyl
silane, polyolefin,
organic initiator and a hydroxy-terminated silicone polymer, and (B) a second
component
comprising a catalyst masterbatch, the second component carried on the first
ribbon. In one
embodiment, the first ribbon comprises a machine-direction groove, and the
second
component is in the form of a ribbon that is fitted into the groove of the
first ribbon. In one
embodiment, the second component is sprayed onto the first ribbon at the time
the first
ribbon is fed into the injection molding machine. In one embodiment the second
component
is dosed directly into the injection molding machine simultaneously with the
feeding of the
first ribbon to the injection molding machine, as opposed to dosing, e.g.,
spraying, the first
ribbon with the second component.
[0013] The tapes and methods of the invention provide an advantage over a
single tape
made by melt blending (A) a polyolefin containing silane functionality in
combination with a
hydroxy-terminated silicone polymer, or a blend of a vinyl silane, polyolefin,
peroxide
organic initiator and a hydroxy-terminated silicone polymer, with (B) a
catalyst masterbatch,
because the single tape made by melt blending the two components will have a
short shelf-
life and likely require the tape to be made at the injection molding site
immediately prior to
use because of limited storage life. The tapes and methods of the invention
will also provide
an advantage over individual tapes of the first and second components and then
individually
feeding these tapes to an injection extruder because simultaneous, consistent
feeding of these
tapes at the proper ratio is problematic at best which, in turn, can lead to
loss of catalyst feed.
[0014] The tapes and methods of this invention allow the delivery of a
consistent mixture
of resin and catalyst to an injection molding extruder. These tapes can be
made off-line and
supplied to a remote molding operation, and these tapes and methods eliminate
the need for
equipment modification.
4
CA 02747894 2016-01-13
77691-109
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure IA is a top plan view of a base resin tape or ribbon.
[0016] Figure 1B is a top plan view of a base resin ribbon comprising a
continuous,
machine-direction groove.
[0017] Figure 1C is a top plan view of a base resin ribbon comprising a
discontinuous or
intermittent, machine-direction groove.
[0018] Figure 1D is a top plan view of a base resin ribbon comprising a
series of cross-
direction grooves.
[0019] Figure 2A is a top plan view of the ribbon of Figure 1B with a
catalyst
masterbatch continuous ribbon fitted into the machine-direction groove.
[0020] Figure 2B is a top plan view of the ribbon of Figure 1B with a
catalyst
masterbatch discontinuous ribbon fitted into the machine-direction groove.
[0021] Figure 3 is a cross-sectional view of a three layer tape
comprising a catalyst
masterbatch layer and a base resin layer separated by a barrier layer.
[0022] Figure 4 is a schematic of a sequence of process steps comprising
dosing a base
resin ribbon with a catalyst as the base resin ribbon layer is fed to an
injection molding
extruder.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Definitions
[0023] All references to the Periodic Table of the Elements refer to the
Periodic Table of
the Elements published and copyrighted by CRC Press, Inc., 2003. Also, any
references to a
Group or Groups shall be to the Group or Groups reflected in this Periodic
Table of the
Elements using the IUPAC system for numbering groups. Unless stated to the
contrary,
implicit from the context, or customary in the art, all parts and percents are
based on weight
and all test methods are current as of the filing date of this disclosure.
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
[0024] The numerical ranges in this disclosure are approximate, and thus
may include
values outside of the range unless otherwise indicated. Numerical ranges
include all values
from and including the lower and the upper values, in increments of one unit,
provided that
there is a separation of at least two units between any lower value and any
higher value. As
an example, if a compositional, physical or other property, such as, for
example, molecular
weight, viscosity, melt index, etc., is from 100 to 1,000, it is intended that
all individual
values, such as 100, 101, 102, etc., and sub ranges, such as 100 to 144, 155
to 170, 197 to
200, etc., are expressly enumerated. For ranges containing values which are
less than one or
containing fractional numbers greater than one (e.g., 1.1, 1.5, etc.), one
unit is considered to
be 0.0001, 0.001, 0.01 or 0.1, as appropriate. For ranges containing single
digit numbers less
than ten (e.g., 1 to 5), one unit is typically considered to be 0.1. These are
only examples of
what is specifically intended, and all possible combinations of numerical
values between the
lowest value and the highest value enumerated, are to be considered to be
expressly stated in
this disclosure. Numerical ranges are provided within this disclosure for,
among other
things, the amount of catalyst in the masterbatch, the relative amounts of
base resin and
catalyst masterbatch in the tape, and various temperatures and other process
ranges.
[0025] As used with respect to a chemical compound, unless specifically
indicated
otherwise, the singular includes all isomeric forms and vice versa (for
example, "hexane",
includes all isomers of hexane individually or collectively). The terms
"compound" and
"complex" are used interchangeably to refer to organic-, inorganic- and
organometal
compounds. The term, "atom" refers to the smallest constituent of an element
regardless of
ionic state, that is, whether or not the same bears a charge or partial charge
or is bonded to
another atom. The term "amorphous" refers to a polymer lacking a crystalline
melting point
as determined by differential scanning calorimetry (DSC) or equivalent
technique.
[0026] "Composition" and like terms mean a mixture or blend of two or more
components. For example, in the context of preparing a silane-grafted ethylene
polymer, a
composition would include at least one ethylene polymer, at least one vinyl
silane, and at
least one free radical initiator. In the context of preparing a cable sheath
or other article of
manufacture, a composition would include an ethylene-vinylsilane copolymer, a
catalyst cure
system and any desired additives such as lubricant, fillers, anti-oxidants and
the like.
6
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
[0027]
"Blend," "polymer blend" and like terms mean a blend of two or more polymers.
Such a blend may or may not be miscible. Such a blend may or may not be phase
separated.
Such a blend may or may not contain one or more domain configurations, as
determined
from transmission electron spectroscopy, light scattering, x-ray scattering,
and any other
method known in the art.
[0028]
"Polymer" means a polymeric compound prepared by polymerizing monomers,
whether of the same or a different type. The generic term polymer thus
embraces the term
homopolymer, usually employed to refer to polymers prepared from only one type
of
monomer, and the term interpolymer as defined below. It also embraces all
forms of
interpolymers, e.g., random, block, homogeneous, heterogeneous, etc. The
terms
"ethylene/a-olefin polymer" and "propylene/a-olefin polymer" are indicative of
interpolymers as described below.
[0029]
"Interpolymer" and "copolymer" mean a polymer prepared by the polymerization
of at least two different types of monomers. These generic terms include both
classical
copolymers, i.e., polymers prepared from two different types of monomers, and
polymers
prepared from more than two different types of monomers, e.g., terpolymers,
tetrapolymers,
etc.
[0030]
"Polyolefin", "olefinic polymer", "olefinic interpolymer", and like terms mean
a
polymer derived from simple olefins. Representative polyolefins include
polyethylene,
polypropylene, polybutene, polyisoprene and their various interpolymers.
[0031]
"Base resin", "base compound" and like terms mean a composition comprising a
polyolefin containing silane functionality in combination with a hydroxy-
terminated silicone
polymer, or a blend of a vinyl silane, polyolefin, optionally an organic
initiator and a
hydroxy-terminated silicone polymer.
[0032]
"Catalyst masterbatch" and like terms mean a composition comprising (i) a
catalyst to promote a reaction of the polyolefin containing silane
functionality with the
hydroxy-terminated silicone polymer, and (ii) a carrier resin. Typically the
carrier resin is
the same as the polyolefin, without the silane functionality, in the base
resin. Alternatively,
the carrier resin can be a resin different from the base resin or a solvent,
i.e., a material that
improves the ability the catalyst to mix with the base polymer in the
injection molding step.
7
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
[0033] "Ribbon", "tape" and like terms mean a narrow band or strip of
material, usually
polymeric material, of indefinite length. Tape and ribbon are often used
interchangeably.
A ribbon can comprise a single layer, or multiple micro-layers such as those
described in
USP 5,094,793. A tape can comprise a single ribbon or two or more ribbons.
[0034] Although the invention is described primarily in terms of a
polyolefin containing
at least one silane functionality and a catalyst masterbatch, the invention
applies to any two
materials or compounds that are reactive with one another under ambient
conditions. As
such, other polymers can be substituted for the polyolefin and other compounds
can be
substituted for the catalyst masterbatch.
Polyolefin
[0035] The density of the polyolefins used in the practice of this
invention, either in the
base resin or in the masterbatch, can range before modification with silane or
other
functionality from 0.855 or less to 0.960 or more grams per cubic centimeter
(g/cm3). The
preferred polyolefins used in both the base resin and the masterbatch
typically have, before
modification with silane functionality, a density of less than 0.930,
preferably less than
0.910, more preferably less than 0.890, even more preferably less than 0.880
and even more
preferably less than 0.870,. The polyolefin copolymers typically have, before
modification
with silane functionality, a density greater than 0.850, preferably greater
than 0.852 and more
preferably greater than 0.855, g/cm3. Density is measured by the procedure of
ASTM D-792.
These relatively low density polyolefins are generally characterized as semi-
crystalline,
flexible and having good optical properties, e.g., high transmission of
visible and UV-light
and low haze.
[0036] The polyolefins used in both the base resin and the masterbatch of
this invention
typically have, before modification with silane functionality, a melt index
greater than 0.10
and preferably greater than 1 gram per 10 minutes (g/10 min). The polyolefins
typically have
a melt index of less than 75 and preferably of less than 20, g/10 min. Melt
index is measured
by the procedure of ASTM D-1238 (190 C/2.16 kg).
[0037] The polyolefins used in both the base resin and the masterbatch of
this invention
can be made by any process, e.g., solution, slurry, gas phase, batch,
continuous, high
pressure, low pressure, etc., and with any catalyst, e.g., Ziegler-Natta,
metallocene,
8
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
constrained geometry, etc. In one embodiment, the polyolefins made with
Ziegler-Natta
catalysts and under high pressure.
[0038] The
polyolefins used in both the base resin and the masterbatch of this invention
include, but are not limited to, ethylene/alpha-olefin interpolymers having an
a-olefin
content of between 15, preferably at least 20 and even more preferably at
least 25, weight
percent (wt%) based on the weight of the interpolymer. These interpolymers
typically have
an a-olefin content of less than 50, preferably less than 45, more preferably
less than 40 and
even more preferably less than 35, wt% based on the weight of the
interpolymer. The
a-olefin content is measured by 13C nuclear magnetic resonance (NMR)
spectroscopy using
the procedure described in Randall (Rev. Macromol. Chem. Phys., C29 (2&3)).
Generally,
the greater the a-olefin content of the interpolymer, the lower the density
and the more
amorphous the interpolymer.
[0039] The
a-olefin is preferably a C3-20 linear, branched or cyclic a-olefin. Examples
of
C3_20 a-olefins include propene, 1-butene, 4-methyl-1 -pentene, 1-hexene, 1-
octene, 1-decene,
1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene. The a-olefins can
also contain
a cyclic structure such as cyclohexane or cyclopentane, resulting in an a-
olefin such as
3-cyclohexy1-1 -propene (allyl cyclohexane) and vinyl cyclohexane. Although
not a-olefins
in the classical sense of the term, for purposes of this invention certain
cyclic olefins, such as
norbornene and related olefins, are a-olefins and can be used in place of some
or all of the
a-olefins described above.
Similarly, styrene and its related olefins (for example,
a-methylstyrene, etc.), and acrylic and methacrylic acid and their respective
ionomers, and
acrylates and methacrylates, are a-olefins for purposes of this invention.
Illustrative
polyolefin copolymers include ethylene/propylene, ethylene/butene, ethylene/1 -
hexene,
ethylene/l-octene, ethylene/styrene, and the like.
Ethylene/acrylic acid (EAA),
ethylene/methacrylic acid (EMA), ethylene/acrylate or methacrylate,
ethylene/vinyl acetate
and the like are also polyolefin copolymers for purposes of this invention.
Illustrative
terpolymers include ethylene/propylene/l-octene,
ethylene/propylene/butene,
ethylene/butene/1 -octene, and ethylene/butene/styrene. The copolymers can be
random or
blocky.
9
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
[0040] More specific examples of olefinic interpolymers useful in this
invention include
very low density polyethylene (VLDPE) (e.g., FLEXOMERS ethylene/l-hexene
polyethylene made by The Dow Chemical Company), homogeneously branched, linear
ethylene/a-olefin copolymers (e.g. TAFMERS by Mitsui Petrochemicals Company
Limited
and EXACT by Exxon Chemical Company), homogeneously branched, substantially
linear
ethylene/a-olefin polymers (e.g., AFFINITY and ENGAGES polyethylene available
from
The Dow Chemical Company), and olefin block copolymers such as those described
in
USP 7,355,089 (e.g., INFUSE available from The Dow Chemical Company). The
more
preferred polyolefin copolymers are the homogeneously branched linear and
substantially
linear ethylene copolymers. The substantially linear ethylene copolymers are
especially
preferred, and are more fully described in USP 5,272,236, 5,278,272 and
5,986,028.
[0041] The polyolefin copolymers useful in the practice of this invention
also include
propylene, butene and other alkene-based copolymers, e.g., copolymers
comprising a
majority of units derived from propylene and a minority of units derived from
another
a-olefin (including ethylene). Exemplary propylene polymers useful in the
practice of this
invention include the VERSIFY polymers available from The Dow Chemical
Company,
and the VISTAMAXX polymers available from ExxonMobil Chemical Company.
[0042] Blends of any of the above olefinic interpolymers can also be used
in this
invention, and the polyolefin copolymers can be blended or diluted with one or
more other
polymers to the extent that the polymers of this invention constitute at least
about 70,
preferably at least about 75 and more preferably at least about 80, weight
percent of the
blend.
Silane Functionality
[0043] The polyolefins used in the base resin of this invention contain, of
course, silane
functionality, e.g., alkoxysilane groups. The silane functionality is included
in the polyolefin
either through grafting or copolymerization. Any silane that will effectively
graft to the
polyolefin or copolymerize with the olefin monomer can be used in the practice
of this
invention. Suitable silanes include unsaturated silanes that comprise an
ethylenically
unsaturated hydrocarbyl group, such as a vinyl, allyl, isopropenyl, butenyl,
cyclohexenyl or
y-(meth)acryloxy allyl group, and a hydrolyzable group, such as, for example,
a
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
hydrocarbyloxy, hydrocarbonyloxy, or hydrocarbylamino group. Examples of
hydrolyzable
groups include methoxy, ethoxy, formyloxy, acetoxy, proprionyloxy, and alkyl
or arylamino
groups. Preferred silanes are the unsaturated alkoxy silanes which can be
grafted onto the
polymer. These silanes and their method of preparation are more fully
described in
USP 5,266,627. Vinyl trimethoxy silane, vinyl triethoxy silane, y-
(meth)acryloxy propyl
trimethoxy silane and mixtures of these silanes are the preferred silane
crosslinkers for is use
in this invention.
[0044] Alternatively, silane copolymers, e.g., SILINKtm poly(ethylene-
co-vinyltrimethoxysilane) copolymer, can be used in place of or in combination
with
polyolefins grafted or otherwise modified with alkoxysilane groups.
[0045] The amount of units derived from the vinyl silane that are either
grafted to or
incorporated into the polyolefin backbone can vary widely depending upon the
nature of the
polyolefin, the silane, the processing conditions, the grafting efficiency,
the ultimate
application, and similar factors, but typically the amount is at least 0.2,
preferably at least
0.5, wt% based on the weight of the polyolefin. Considerations of convenience
and economy
are usually the two principal limitations on the maximum amount of units
derived from a
vinyl silane grafted to or incorporated into the polyolefin backbone, and
typically the
maximum amount of such units does not exceed 5, preferably it does not exceed
3, wt%
based on the weight of the polyolefin.
[0046] The vinyl silane is grafted to the polyolefin by any conventional
method, typically
in the presence of a free radical initiator e.g. peroxide, or by ionizing
radiation, etc. Organic
initiators are preferred, such as any one of the peroxide initiators, for
example, dicumyl
peroxide, di-tert-butyl peroxide, t-butyl perbenzoate, benzoyl peroxide,
cumene
hydroperoxide, t-butyl peroctoate, methyl ethyl ketone peroxide, 2,5-dimethy1-
2,5-di(t-butyl
peroxy)hexane, lauryl peroxide, and tert-butyl peracetate. The amount of
initiator can vary,
but it is typically present in an amount of at least 0.01, preferably at least
0.03, wt%.
Typically, the initiator does not exceed 0.15, preferably it does not exceed
about 0.10, wt%.
The weight ratio of vinyl silane to initiator also can vary widely, but the
typical vinyl
silane:initiator weight ratio is between 10:1 to 150:1, preferably between
18:1 and 100:1.
The polyolefin can be grafted with the vinyl silane either (1) before the base
resin is
formulated, e.g., the embodiment in which the base resin comprises a
polyolefin containing
11
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
silane functionality in combination with a hydroxy-terminated silicone
polymer, or (2) after
the base resin is formulated, e.g., the embodiment in which the base resin
comprises a blend
of a vinyl silane, polyolefin, organic initiator and a hydroxy-terminated
silicone polymer. In
the latter embodiment, the grafting occurs after feeding the tape to the
injection molding
machine. In the former embodiment, any conventional method can be used to
graft the silane
crosslinker to the polyolefin, and one preferred method is melt blending in a
reactor extruder,
such as a twin-screw extruder or a Buss kneader at appropriate temperatures
depending on
the polymer and the initiator used.
Hydroxy-Terminated Silicone Polymer
[0047] The
selection of 'suitable hydroxy-terminated silicone polymers for use in this
invention is limited to those silicone polymers that can be blended with
either (1) a
polyolefin containing silane functionality, or (2) a mixture of vinyl silane,
polyolefin and
peroxide. This ability to mix will typically be affected by the viscosity of
the hydroxy-
terminated silicone polymer which generally relates to its molecular weight.
Typically, the
viscosity of the hydroxy-terminated silicone polymer ranges from 80 to about
2500
centistokes (cs). Such viscosities are typical for silicone softeners or
lubricants found in the
market.
[00481 Non-
limiting examples of useful hydroxy-terminated silicone polymers include
those of the following formula (I):
CH3 CH3 CH3
HO Si _____________________ 0 (Si 0) __________________ OH
CH3 CH3 CH3
(I)
in which "n" is from 3 to 20, although other hydroxy-terminated silicone
polymers may be
employed within the scope of the present invention. Notably, silicone polymers
according to
the foregoing formula (I) will have a viscosity in the range of from 80 to
about 2500 es.
12
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
Catalyst
[0049] The reaction of the polyolefin containing silane functionality with
the hydroxy-
terminated silicone polymer is accelerated with a cure catalyst, and any
catalyst that will
provide this function can be used in the practice of this invention. These
catalysts generally
include organic bases, carboxylic acids and organometallic compounds including
organic
titanates and complexes or carboxylates of lead, cobalt, iron, nickel, zinc
and tin. Illustrative
catalysts include dibutyl tin dilaurate, dioctyl tin maleate, dibutyl tin
diacetate, dibutyl tin
dioctoate, stannous acetate, stannous octoate, lead naphthenate, zinc
caprylate and cobalt
naphthenate. Tin carboxylates such as dibutyl tin dilaurate, dimethyl hydroxy
tin oleate,
dioctyl tin maleate, di-n-butyl tin maleate and titanium compounds such as
titanium
2-ethylhexoxide are particularly effective for use in this invention.
Additives
[0050] The polymeric materials, e.g., the base resin and the catalyst
masterbatch, of this
invention can comprise additives other than or in addition to cure catalysts.
For example,
such other additives include UV-stabilizers and processing stabilizers such as
trivalent
phosphorus compounds. The UV-stabilizers include hindered phenols such as
Cyasorb
UV2908 and hindered amines such as Cyasorb UV 3529, Hostavin N30, Univil 4050,
Univin
5050, Chimassorb UV 119, Chimassorb 944 LD, Tinuvin 622 LD and the like. The
phosphorus compounds include phosphonites (PEPQ) and phosphites (Weston 399,
TNPP,
P-168 and Doverphos 9228). The amount of UV-stabilizer is typically from about
0.1 to
0.8%, and preferably from about 0.2 to 0.5%. The amount of processing
stabilizer is
typically from about 0.02 to 0.5%, and preferably from about 0.05 to 0.15%.
[0051] Still other additives include, but are not limited to, antioxidants
(e.g., hindered
phenolics such as Irganox 1010 made by Ciba Geigy Corp.), cling additives
(e.g.,
polyisobutylene), anti-blocks, anti-slips, pigments, fillers (clear if
transparency is important
to the application), surfactants, and flame retardants. In-process additives,
e.g. calcium
stearate, water, etc., may also be used. These and other potential additives
are used in the
manner and amount as is commonly known in the art.
13
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
[0052] Carbon black is a common filler and/or pigment for the polymeric
materials used
in the practice of this invention. Any carbon black can be used and for those
applications in
which the finished polymeric material requires some measure of conductivity,
e.g., cable
coverings, the carbon black preferably exhibits at least a low level of
electrical conductivity.
For example, if the polymeric material is to be used as a semiconductor shield
for a cable,
then preferably the carbon black will reduce the electrical conductivity of
the polymeric
material to less than 500 ohm-meter, more preferably to less than 250 ohm-
meter, and even
more preferably to less than 100 ohm-meter.
[0053] Examples of carbon blacks that can be used in the practice of this
invention
include furnace black, acetylene black, kettchen black, channel black and
thermal black.
Commercially available carbon blacks include N550 carbon black sold by Cabot
Corporation. The amount of carbon black admixed with the base resin, if any,
is typically
from about 20 to 90 parts by weight and preferably from about 40 to 80 parts
by weight.
Compounding the Base Resin and the Catalyst Masterbatch
[0054] Both the base resin and the catalyst masterbatch are compounded
using standard
equipment and techniques. Examples of compounding equipment are internal batch
mixers,
such as a BanburyTM or BoilingTM internal mixer. Alternatively, continuous
single, or twin
screw, mixers can be used, such as FarrelTM continuous mixer, a Werner and
PfleidererTM
twin screw mixer, or a BussTM kneading continuous extruder. The type of mixer
utilized, and
the operating conditions of the mixer, will affect properties of the material
under mixture,
such as viscosity, volume resistivity, and extruded surface smoothness.
[0055] In a preferred embodiment, the formulation of the base resin, either
(1) a
polyolefin containing silane functionality and a hydroxy-terminated silicone
polymer, or (2) a
polyolefin, vinyl silane, an optional organic initiator, and hydroxy-
terminated silicone
polymer, are added to a mixing vessel in any order and in the appropriate
amounts, and
mixed under non-reactive conditions to form an essentially homogeneous mixture
of the
components. The amount by weight of polyolefin (with or without silane
functionality) to
hydroxy-terminated silicone polymer in the mixture is typically in the range
of 50:50, more
typically 80:20 and even more typically 95:5.
14
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
[0056] In the formulation of the catalyst masterbatch, a large amount of
cure catalyst is
mixed with a representative portion of the carrier polymer, typically the same
polyolefin used
in the base resin but without silane functionality, to form a substantially
homogeneous
mixture. The amount of catalyst to carrier resin in the mixture can vary
widely, but is
typically 10:90, more typically 5:95 and even more typically 3:97.
Manufacture of the Tape
[0057] After the base resin is formed into an essentially homogeneous
mixture, including
any additives, it is extruded into a tape, i.e., a continuous strip, and
allowed to solidify. The
dimensions of the tape can vary widely, but typical tapes have a width
dimension of between
50 and 10 millimeters (mm), a thickness dimension of between 2 and 20 mm, and
an
indefinite length, i.e., a length of choice that is limited only by the volume
of mixture
extruded. The tape can have any one of a number of different configurations.
Figure 1A
illustrates base resin tape 10 in an essentially smooth and flat configuration
and comprising a
single layer. Alternatively and not shown, tape 10 can comprise a stack of
multiple micro-
layers which, in the aggregate, have a thickness comparable to that of single
layer tape 10.
Such tapes are well-known in the art, and are illustrated in USP 5,094,793.
[0058] Figure 1B shows the tape 10 configured with continuous machine-
direction
groove 11a. Figure 1C shows tape 10 configured with intermittent or
discontinuous
machine-direction groove 1 lb. Figure 1D shows tape 10 configured with cross-
direction
grooves 11 c. The groove or grooves can also be at other angles to the machine
direction of
the ribbon. The depth, cross-section configuration (e.g., V-shaped, U-shaped,
etc.), shape
(e.g., straight, serpentine, etc.,), etc., of the groove can vary to choice
with the understanding
that the groove is preferably configured to received and physically (as
opposed to chemically
or adhesively) hold the catalyst masterbatch component of the finished tape
product. For
reasons of ease of manufacture, equipment selection and the like, preferably
tape 10 is
configured with a continuous, machine-direction groove.
[0059] Typically, the catalyst masterbatch is also extruded as a continuous
strip, typically
a strip much smaller in width and physically adjoined to the tape in any
suitable manner.
Here too, the strip can comprise a single layer or a stack of micro-layers. If
the tape is not
configured with a groove or similar device to receive and hold the catalyst
masterbatch, then
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
typically it is simply laid upon the solidified base resin tape and through
the combination of
(i) any inherent tackiness between the base resin tape and catalyst
masterbatch ribbon, and
(ii) the physical restraint resulting from the collection of the tape and
ribbon into a reel.
Alternatively, or in addition to, the catalyst masterbatch ribbon can be
pressed, with or
without heating, against the base resin tape, e.g., by passing the combination
of the two
through one or more sets of pinch rollers, to promote the joining of the two
components. If
heat is used, then only sufficient heat to soften one or both of the base
resin tape or catalyst
masterbatch ribbon is used. Full melting of either the base resin tape or the
catalyst
masterbatch ribbon is not desirable.
[0060] Similarly, an adhesive can be employed to fix the catalyst
masterbatch to the base
resin tape. If an adhesive is used, then only an amount sufficient to promote
the adhesion of
the catalyst masterbatch ribbon to the base resin tape is employed. The
adhesive can be
employed congruent with the catalyst masterbatch ribbon, or intermittent with
it. The choice
of adhesive, if any, is not critical to the practice of this invention and as
such, any adhesive
that does not materially adversely impact the desired polymeric properties can
be used.
Typically, the adhesive is a pressure-sensitive adhesive; preferably a natural
or synthetic
rubber used either alone or in combination with one or more other adhesives.
The acrylate
and methacrylate-based adhesives are also useful in the practice of this
invention. The
adhesive can be applied as a coating, separate ribbon (e.g., lamination), or
by any other
convenient method. It can be applied to the full surface area of the base
resin tape, or limited
to the groove or grooves, or applied to the catalyst masterbatch ribbon, or
both.
[0061] If the base resin tape is configured with a groove or similar
device, particularly a
continuous, machine-direction groove, then the catalyst masterbatch is sized
for and extruded
in a manner that allows insertion into the groove. Here too, insertion of the
catalyst
masterbatch ribbon into the groove on the base resin tape can be aided through
the
application of pressure, e.g., the use of one or more sets of pinch rollers.
Figure 2A
illustrates continuous catalyst masterbatch ribbon 12 inserted into continuous
machine-
direction groove lla (not shown) of tape 10. Although the catalyst masterbatch
strip can also
be of indefinite length, it can also be much shorter and fitted to the base
resin tape on an
intermittent or discontinuous basis as illustrated in Figure 2B. The catalyst
masterbatch is
fitted to the base resin tape such that it represents 3 to 5 wt% of the
combined weight of the
16
CA 02747894 2011-06-21
WO 2010/074914 PCT/US2009/066562
base resin and catalyst masterbatch so as not to interfere with crosslinking
efficiency of the
base resin tape.
[0062] In an alternative embodiment base resin tape 10 and catalyst
masterbatch
ribbon 12 are separated by intermediate barrier layer 13 as illustrated in
Figure 3. Here too,
the barrier resin layer can be a single layer or a stack of micro-layers. This
intermediate layer
can comprise any material that will delay the contact of the catalyst of the
masterbatch with
the base resin tape. Such materials include, but are not limited to,
functional copolymers,
e.g., nylon, Saran, ethylene vinyl alcohol copolymer, and the like. In this
embodiment, the
final product tape, i.e., the tape comprising the three layers of base resin,
barrier resin and
catalyst masterbatch, is typically a multilayered structure with each layer of
approximately
the same width and length although the thickness of each layer is likely
different with the
base resin layer the thickest and the catalyst masterbatch layer the thinnest.
The presence of
the intermediate barrier layer enhances the life of the final product tape by
preventing pre-
mature reaction (scorching) of the polyolefin containing silane functionality
and the hydroxy-
terminated silicone polymer until the tape is fed to an extruder and the tape
components melt
blended with one another prior to extrusion.
[0063] In another embodiment the catalyst masterbatch, or simply and
preferably just
catalyst, is dosed onto the base resin ribbon just prior to or simultaneously
with the feeding
of the ribbon to an extruder. This embodiment is illustrated by the schematic
of Figure 4.
Base resin ribbon 10 is fed directly to extruder 16. As the base resin ribbon
is fed into the
injection molding machine, the tape is dosed, e.g., sprayed, with catalyst 14
from pump or
other delivery device 15. Since shelf life of the final product tape, e.g.,
base resin ribbon and
catalyst, is not a concern in this embodiment, neither a carrier resin nor a
barrier layer is
required. However, this embodiment does encourage preparation of the final
tape product at
the site of the extrusion or molding operation (although the tape will have a
limited shelf life
under the ambient conditions that prevail outside of the extruder).
[0064] Alternative dosing methods include passing the base resin tape
through a bath
comprising the catalyst prior to feeding the tape to an injection molding
machine, depositing
catalyst in the form of a full or partial coating onto the base resin tape by
any coating
technique, and feeding the catalyst, either neat or in the form of a
masterbatch, directly into
the injection molding machine apart from but simultaneously with or prior to
the feeding of
17
CA 02747894 2016-01-13
77691-109
the base resin tape to the injection molding machine. Conventional injection
molding
machines typically have a zone or compartment in which components of a
formulation can be
homogeneously blended before transferred to the mold or extruder, and to this
zone or
compartment is where the base resin tape and catalyst are fed.
[00651 Current rubber injection molding technology uses tapes made from
pre-compounded and filly homogenized peroxide based materials. While these
materials
have a relatively good shelf life when stored at room temperature, this
approach is not useful
with materials that inherently reactive materials over a broad range of
temperatures. The
tapes and processes of this invention are particularly useful in the field of
moisture-curable or
hydroxy-silicone cured resins systems and applications.
[00661 Although the invention has been described in considerable detail
through the
preceding description, drawings and examples, this detail is for the purpose
of illustration.
The scope of the claims should not be limited by the preferred embodiments set
forth in
the examples, but should be given the broadest interpretation consistent with
the description
as a whole.
18
